Swiss Needle Cast

This disease will ruin the current forestry practice of large single species plantations and require a rethinking the intricacies of the forest as an environment. The pathogen is a fungus, Latin name, Phaeccryptopus gaeumannii, is native to North America and is hosted by Douglas-fir trees. Typically a healthy Douglas fir will carry four years worth of needles. However, Swiss Needle Cast causes a great number of trees to loose all but the current years needles. The trees turn yellow in as little as eight months following infection, and some trees die in as little as eight years. A scientific flyover of the coastal range in the spring of 1996 revealed one hundred thirty thousand acres of the Douglas-fir population infected. So with that in mind the some I speak of could be a conservative fifteen thousand acres. Some not all. Other populations can live thirty years and more, with the fungus. While other infected trees maintain a normal-appearing crown with its full four years of needles. This leads many researchers to think there may exist a tolerance in the species.

There are many things that researchers in both the public and private know about the disease. They know that in the trees that do not die there is slowed growth. They know that the symptoms are more obvious in younger trees of 10 to 30 years of age. They know it is wind-borne and flowers in the wet winter and spring. They know that the tree won't get over it as if it were a cold. They know that the area of infection is much larger than that which was mapped from the air last year. What they do not know, is why the disease is so active now. Actually of the few foresters I've spoken with, the common belief is that there are a variety of factors. One being tainted seed stock, seedlings that were grown from trees outside of the coast range. Another is the single species plantations that have replaced the natural Spruce, Hemlock, Cedar and Fir forests. In the natural forest Douglas fir trees were a smaller component, scattered and spaced further apart. Even a recent change in weather patterns is being considered.

This is no easy infection to cure and so far nothing has seemed to work on a forest wide scale. There have been attempts to treat with fungicides, systemic nutrient mixtures and additions of fertilizer applications. None of these methods have shown any success or promise of success in treating infected trees. There is a positive. Kate Kavanagh in Clatsop County has been doing studies to see if infected trees are more susceptible to infestation from insects. So far in her research that does not appear to be the case. Presently, the only way to fight this is by changing the current forest practices. The thinning of stands of Douglas fir and the reintroduction of a multi-species forest with Spruce, and Hemlock is the best change to be made. This will of course curtail timber production. The fact that Douglas fir is the main tree replanted has to do with its ability to grow fast and produce clear straight timber in a short time. The reduction in the numbers of Douglas fir would impact the forest product industry's ability to supply the demand for those products. It takes a much longer time to grow Spruce and Hemlock does not posses the straight grain for lumber that is desirable.

The various agencies involved are studying everything about Swiss Needle Cast. The pathogen is being studied from every angle; the genetics of the Douglas fir and the variation in resistance within the species is probably the best single way to address this disease. But the biology of the fungus and its relationship with Douglas fir is also under going research. I believe that many of the current studies for 1997 will be available soon. If you desire to know more about this contact the




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Last Modified: Friday, 06-Apr-2007 23:22:42 EDT